The present invention relates to building materials. It particularly relates to novel compositions for the preparation of concrete building materials and to building blocks prepared from such compositions. The invention further relates to novel low density concrete building materials having high resistance to cracking, good insulating properties and good overall strength and to building blocks prepared therefrom.
The use of Portland cement in the preparation of concrete blocks for building and other purposes is well known. These blocks have good strength but are heavy and have poor insulating properties. Furthermore, although these blocks have good compressive strength, they have poor tensile strength and tend to eventually develop cracks under stress. The addition of materials to Portland cement to reduce the weight of blocks made from the cement, to improve the insulating properties of such blocks, and to impart other desirable properties is also well known in the art. The addition of sawdust or other low density material to reduce the weight of the concrete blocks and to improve their insulating properties is shown in U.S. Pat. Nos. 889,569, 1,309,038, 1,463,123, 1,484,370, 2,057,330, 2,592,345, 2,899,325, 3,264,125, and 4,166,745. Besides sawdust, other low density materials such as wood shavings, bark particles, cellulosic fibers, asbestos and artificial fibers have been used.
Substances such as silicates, chlorides, nitrates and sulfates have been added to Portland cement to increase the binding of the particles in the concrete. The use of such additives is shown in U.S. Pat. Nos. 1,309,296, 1,463,123, 1,484,370, 2,057,330, 2,592,345, 3,264,125, and 3,311,483.
Despite these various improvements in concrete building materials, whether they contain or do not contain any of the various materials described above, blocks made from such materials do not weather well and eventually develop cracks under stress. In view of this, it is an object of the present invention to provide a concrete building material which overcomes the above-mentioned deficiencies. Other objects and features will be in part apparent and in part pointed out hereinafter. The invention accordingly comprises the products hereinafter described, the scope of the invention being indicated by the subjoined claims.